1What are the two major parts of the eukaryotic cell cycle?
Interphase and M phase
2What are the phases of interphase?
G1, S, and G2
3What happens in G1 phase?
Primary growth phase (longest phase)
4What happens in S phase?
DNA replication
5What happens in G2 phase?
Organelles replicate and microtubules organise
6What happens in M phase?
Mitosis (nuclear division)
7What is cytokinesis?
Separation/cleavage into two new cells
8What is mitosis?
Cell division producing two genetically identical daughter cells
9What are the five phases of mitosis?
Prophase, prometaphase, metaphase, anaphase, and telophase
10What happens in prophase?
Chromosomes condense; spindle begins forming; nuclear envelope breaks down
11What happens in prometaphase?
Microtubules attach to kinetochores and chromosomes move toward the cell centre
12What happens in metaphase?
Chromosomes align along the metaphase plate
13What is the metaphase plate?
Not a physical structure; the future axis of cell division
14What happens in anaphase?
Sister chromatids separate and move to opposite poles
15What key molecular event triggers anaphase?
Removal of cohesin proteins
16What are the two types of anaphase movement?
Anaphase A (chromatids move to poles) and Anaphase B (poles move apart)
17What happens in telophase?
Spindle disassembles; nuclear envelopes reform; chromosomes uncoil; nucleolus reappears
18How does cytokinesis occur in animal cells?
Actin filament constriction forms a cleavage furrow
19How does cytokinesis occur in plant cells?
A cell plate forms between the nuclei
20What is the centromere responsible for?
Accurate segregation of replicated chromosomes during mitosis and meiosis
21What is the kinetochore?
Structure at the centromere where microtubules attach
22Where do microtubules attach to chromosomes?
At the kinetochore
23What is special about centromeric chromatin?
Defined by histone complement (CENP-A), not DNA sequence
24What is CENP-A (CenH3)?
A centromere-specific protein homologous to histone H3
25What are the four chromosome types based on centromere position?
Telocentric, acrocentric, submetacentric, and metacentric
26What is meiosis?
Cell division that produces genetically different haploid cells
27How many rounds of division occur in meiosis?
Two (meiosis I and meiosis II)
28What stages occur in both meiosis I and meiosis II?
Prophase, metaphase, anaphase, and telophase
29What is synapsis?
Pairing of homologous chromosomes in early prophase I
30What forms during synapsis?
Synaptonemal complexes
31What are synaptonemal complexes also called?
Tetrads or bivalents
32What happens in meiosis prophase I?
Chromosomes condense; spindle forms; synapsis occurs; crossing over occurs
33What is crossing over?
Genetic recombination between non-sister chromatids
34What is the purpose of crossing over?
Exchange chromosomal material between homologues
35What are chiasmata?
Sites of crossing over
36Until when are chiasmata maintained?
Until anaphase I
37What happens in metaphase I?
Homologous pairs align side-by-side at the metaphase plate
38How do microtubules attach in metaphase I?
Attach to each homologue (not each sister chromatid)
39What is independent assortment?
Random orientation of maternal vs paternal homologues on the spindle
40What happens in anaphase I?
Homologous chromosomes separate to opposite poles
41Do sister chromatids separate in anaphase I?
No, they remain attached at centromeres
42What is the result at each pole after anaphase I?
A haploid set of chromosomes (one chromosome from each homologous pair)
43What happens in telophase I?
Nuclear envelopes may reform; sister chromatids are no longer identical
44Does cytokinesis always occur after telophase I?
No, it may or may not occur
45What is meiosis II similar to?
A mitotic division
46What happens in metaphase II?
Chromosomes align on the metaphase plate
47What happens in anaphase II?
Sister chromatids separate and move to opposite poles
48What is the final result of meiosis?
Four genetically different haploid cells
49What does mitosis produce?
Genetically identical daughter cells
50What does meiosis produce?
Genetically different haploid cells
51What are 4 distinct features of meiosis compared to mitosis?
Homologous pairing/crossing over; homologues separate in meiosis I; no DNA replication between meiosis I and II; produces haploid cells
52What is nondisjunction?
Failure of chromosomes to separate properly during meiosis
53What are aneuploid gametes?
Gametes with missing or extra chromosomes
54What is the most common cause of spontaneous abortion (related to meiosis errors)?
Aneuploid gametes due to nondisjunction
55What condition is caused by monosomy X?
Turner syndrome